Among ship radars, a low priced compact radar, especially such as a radome type radar, has a short antenna length that causes a horizontal beam width to widen, and as a result there has been a problem with low resolution in an azimuth direction. In such case where the resolution in the azimuth direction is low, a target is displayed on a radar screen in a manner of being extended in the azimuth direction more than an appropriately scaled size, therefore, there has been a problem that a visibility of the target on the radar screen degrades; for example, two aligned targets may be superimposed with each other and recognized as one.
Although various methods of improving the azimuth resolution have been proposed, such as using a phased array antenna and a MUSIC algorithm, expensive hardware, such as an antenna, and a complex equipment have been impediments to adoption and, currently, the above methods are difficult to be adopted for low priced compact radar.
Meanwhile, various methods of improving the visibility of the target on the radar screen by improving a method of processing the received signal have also been proposed. For example, JP10-038997A discloses a radar image processing device that allows an easy observation of a radar image by filtering an original signal through a low pass filter to enlarge the radar image. Implementation of such a method of improving the signal processing method can be realized at a lower cost than the method of improving the function of an antenna itself (e.g., the phased array antenna and the MUSIC algorithm), and therefore, it is considered easy to apply to compact and low priced radar.
Meanwhile, the configuration disclosed in JP10-038997A is for enlarging the radar image in the azimuth direction, and therefore cannot solve the problem that the two targets aligned in the azimuth direction are superimposed with each other and perceived as one. Thus, with the configuration disclosed in JP10-038997A, an effect of improving the azimuth resolution of compact radar cannot be expected.
The present invention is made in view of the above situation, and a main object thereof is to provide a radar signal processing device where resolution is improved by simple signal processing, without requiring expensive hardware and a complex system.